Difference between revisions of "Understanding HyperSync and High Speed Sync"

Revision as of 10:13, 26 June 2013

This section describes how HyperSync and High Speed Sync work at a basic level. Read the HyperSync Setup section for more detailed information on how to adjust HyperSync for your configuration.

When shooting with flash, there are different methods of synchronizing the flash with a camera’s shutter. These methods depend primarily on the shutter speed and flashes you use.

While the flash appears instantaneous to our eyes, it actually has duration and variance. These are important to the camera’s sensor, especially at faster shutter speeds.

At shutter speeds slower than X-Sync, usually 1/200 or slower, a normal flash of light is all that is required; the first curtain of the shutter opens, the flash fires for its flash duration, and the second curtain of the shutter closes.

At shutter speeds faster than X-Sync (usually 1/250 through 1/8000) the time between the shutter’s first curtain opening and second curtain closing is not long enough for a normal flash of light to complete its duration. At the fastest shutter speeds, the shutter’s curtains are moving at the same time, exposing a moving slit of light across the sensor. At these shutter speeds, other flash techniques must be used.

High Speed Sync (HSS or Auto-FP sync) begins pulsing the flash before the first curtain opens and continues to pulse it until after the second curtain closes. From the camera’s perspective this pulsed light appears as continuous light during the exposure. HSS uses a lot of energy, however, which means there is less light available for the image, and is usually only available in lower powered Speedlites/Speedlights. Syncing up to 1/8000 is possible, but the flash must be very close to the subject.

HyperSync uses a normal flash of light, which has much more energy in it compared to pulsed HSS. HyperSync also uses precision timing to align the flash’s duration and output curve with the moving shutter curtains. This allows more light in the image than HSS can provide, and works with higher powered flashes like studio flash packs and monolights. Different flash and camera combinations yield different shutter speed and light output performance, but most combinations will get worthwhile benefits using HyperSync.

Other techniques, like the "HSS Hack" (with or without a manually dialed in delay), can sometimes get a normal flash of light from a studio pack into an exposure taken at faster shutter speeds, but these methods are less precise than HyperSync, lack automation, and are more limited to which camera and flash combinations yield usable results.

How Does a Flash Work?

A flash is designed to emit a very intense light for a short duration of time. This is done by filling a flashtube with xenon gas, and then using a charged capacitor to energize the xenon with a very high amount of electrical current. This produces the light that flashes use to illuminate a scene. You can visualize a single flash event as “light over time,” plotted as a curve. The peak has the highest amount of energy emitted but energy continues to be emitted at a decreasing rate so long as the xenon gas is energized. This drop in energy (and therefore light output) creates the “tail” of the curve.

While appearing to be instantly turned on and instantly turned off again, a flashtube can be excited for anywhere from 1 microsecond to tens of milliseconds. Most consumer flashes usually average around 1 millisecond, with some being longer, and some being shorter.

How Does a Shutter Work?

A camera’s shutter has two curtains that cover the sensor. When you press the shutter button, the first curtain moves, exposing the sensor. Next, the second curtain moves, finishing the exposure. Your first curtain opens all the way before the second curtain starts to move. This fully exposes the camera’s sensor. Your camera has a limit where it can fully open its shutter and capture a normal flash flash duration across the entire sensor all at once. This is your camera’s X-Sync limit.

Shutter speeds above X-Sync act differently. The first curtain begins to move downwards. Before they reach the bottom, the second curtain begins to move. This creates a moving slit.

The faster the shutter speed, the smaller the slit:

X-Sync - Flash behavior with normal sync limits

A flash directly connected to a camera

Your camera has a limit where it can fully open its shutter and capture flash across the entire sensor all at once. This is your camera’s X-Sync limit.

A camera triggering a flash at X-Sync follows this timeline:

1. The shutter button is pressed.
2. Several milliseconds of time pass. This is called lag time. The amount of lag time varies from camera to camera.
3. The first curtain moves from the top of the sensor to the bottom.
4. The camera’s sensor is exposed.
5. Some microseconds of time pass. The camera triggers its PC terminal and the center sync pin on the hot shoe.
6. The flash emits light for its flash duration. The time this happens can be any amount of time up to a few milliseconds.
7. The second curtain moves from the top of the sensor to the bottom.
8. The second curtain in the camera closes and both curtains reset to the top of the sensor

Shutter speeds above X-Sync work differently. A camera triggering a flash above X-Sync follows this timeline:

1. The shutter button is pressed.
2. Several milliseconds of time pass. This is called lag time. The amount of lag time varies from camera to camera.
3. The first curtain begins to move from the top of the sensor to the bottom.
4. The camera’s sensor is exposed.
5. Before the first curtain reaches the bottom of the sensor, the second curtain begins to move. The space between the first and second curtain is a small slit that moves across the sensor. The faster your shutter speed, the smaller the slit becomes.
6. The first curtain reaches the bottom of the sensor.
7. The camera triggers its PC terminal and the center sync pin on the hot shoe. (Many cameras do not provide this sync output above X-Sync.)
8. The flash emits light for its flash duration. The time this happens can be any amount of time up to a few milliseconds.
9. The moving slit is exposed to the flash.
10. The second curtain in the camera closes and both curtains reset to the top of the sensor

When a camera connected directly to a flash via sync cable is used above X-Sync the second curtain blocks part of the sensor from being exposed to light. This shows up as a black band, or clipping.

Flashes with a long flash duration can show clipping, even at X-Sync. Cameras with a slow moving shutter can show clipping at X-Sync.

A Flash Triggered Remotely by a Center Pin Triggered Radio Trigger

Standard radio triggers can introduce bottom-frame shutter shadowing, or "clipping" in your image even at your camera's sync limit. 5D Classic 1/200th, Plus II radios

Center Pin Triggered radio triggers get their sync signal from the center pin on your camera (X-Sync pin). It takes time for radio to transmit to a receiving radio. That signal then is processed. This transmission time and processing is called “radio propagation delay.”

A camera and flash using center-pin radio triggers follow this timeline:

1. The shutter button is pressed.
2. Several milliseconds of time pass. This is called lag time. The amount of lag time varies from camera to camera.
3. The first curtain moves from the top of the sensor to the bottom.
4. The camera’s sensor is exposed.
5. Some microseconds of time pass. The camera triggers its PC terminal and the center sync pin on the hot shoe.
6. The transmitting center pin triggered radio in the top shoe receives this X-Sync signal.
7. The transmitting radio processes this X-Sync signal.
8. The transmitting radio sends out a trigger command.
9. The receiving radio receives the signal.
10. The receiving radio processes the received radio signal.
11. The receiving radio triggers the attached flash.
12. The second curtain moves a small amount from the top of the sensor towards the bottom
13. The flash emits light for its flash duration. The time this happens can be any amount of time up to a few milliseconds.
14. The second curtain in the camera closes and both curtains reset to the top of the sensor

The timing sequence has tighter tolerances at X-Sync compared to slower speeds. This tighter tolerance and the radio processing delay moves the moment the sensor sees the flash. Since the second curtain has started to move a small bit, you get shadowing or clipping in your exposure. Flashes with long durations can show clipping at X-Sync. Cameras with slow shutters can show clipping at X-Sync. To get rid of clipping, you may have to use a slower shutter speed.

The PlusX, Plus III, or MultiMAX have a mode to reduce this delay, called Transmit Only. A receiving Plus III can use FAST mode to reduce processing time.

High Speed Sync

High Speed Sync (HSS) is a Canon technique for syncing flash above X-Sync. HSS is called Auto-FP in the Nikon system. This is a speedlight-only technique that pulses light above X-Sync. This appears to the camera as a continuous light at faster shutter speeds.

A camera and flash using HSS/Auto-FP follow this timeline:

1. The shutter button is pressed.
2. Several milliseconds of time pass. This is called lag time. The amount of lag time varies from camera to camera.
3. The speedlight begins to pulse light just before the first curtain begins to move.
4. The first curtain begins to move from the top of the sensor to the bottom.
5. The camera’s sensor is exposed.
6. Before the first curtain reaches the bottom of the sensor, the second curtain begins to move. The space between the first and second curtain is a small slit that moves across the sensor. The faster your shutter speed, the smaller the slit becomes.
7. The speedlight continues to pulse.
8. The first curtain reaches the bottom of the sensor.
9. The second curtain in the camera closes and both curtains reset to the top of the sensor.
10. The speedlight stops pulsing.

HSS/Auto FP requires a speedlight. Studio strobes are not capable of pulsing light. HSS requires special timing information from the camera. This information is communicated through the TTL pins of a camera's hot shoe. A normal studio flash cannot perform the light pulse technique.

HSS exposures will not be as bright as standard single-pop flashes, because the available energy is divided among all the pulses over exposure time. The pulsed light requires more energy than non-pulsed flash. Flashes using HSS may need to be positioned closer to a subject.

HyperSync

A normal, non-HSS flash is more efficient at delivering light to a subject than an HSS (pulsed) flash. As a result, flashes may be positioned farther from a subject.

HyperSync uses special camera communication to trigger a normal flash before the first curtain opens. It can also eliminate the delay introduced by a typical radio trigger. The timing can be optimized for some flashes based on the user’s wishes.

A camera triggering a flash with HyperSync follows this timeline:

1. The shutter button is pressed.
2. Several milliseconds of time pass. This is called lag time. The amount of lag time varies from camera to camera.
3. The attached MiniTT1 or FlexTT5 senses exactly when the shutter will fire, and then fires the flash early.
4. The first curtain begins to move from the top of the sensor to the bottom.
5. The camera’s sensor is exposed.
6. Before the first curtain reaches the bottom of the sensor, the second curtain begins to move. The space between the first and second curtain is a small slit. The faster the shutter speed is set the smaller the slit will become.
7. The first curtain reaches the bottom of the sensor.
8. The camera triggers its PC terminal and the center sync pin on the hot shoe.

HyperSync requires a ControlTL transmitter like the Nikon MiniTT1 and FlexTT5 or Canon MiniTT1 and FlexTT5. Optimizing HyperSync Automation require a ControlTL receiver like the PowerMC2, PowerST4, or AC9 AlienBees Adapter. All transmitter HyperSync adjustments are made in the PocketWizard Utility on the HyperSync/HSS Tab. Any PocketWizard radio can be used as a receiver and be triggered from the ControlTL transmitter's HyperSync timing. You will see the best results using a ControlTL receiver.

There are two methods of using HyperSync Automation available on a ControlTL receiver: Reduced Clipping and Highest Energy. The two methods choose different flash firing times relative to the camera's shutters opening.

Reduced Clipping

Reduced Clipping attempts to keep bottom frame clipping out of your images. Reduced Clipping may result in a gradient across the image. Gradation means the photo is lighter at the bottom and darker at the top. The results are very usable in many situations.

Reduced Clipping benefits photographers:

• Shooting outdoors where the sky is a major factor in the top part of the image
• Using aperture priority in conditions that cause the shutter speed to go above X-sync
• In any situation where the full frame must be used and cropping is not an option

"Reduced Clipping" is selected on the ControlTL receiver, as shown in on the All ControlTL Radios – HyperSync Automation page. This is the factory default setting.

• You can use Reduced Clipping-style HyperSync manually with a non-ControlTL compatible flash by following the directions for the FlexTT5 P2 Port and trying to eliminate clipping at your highest shutter speeds.
• You can attempt to use Reduced Clipping-style HyperSync manually with a radio receiving on a Standard Channel (meaning a (Plus II, Plus III, PlusX, MultiMAX, FlexTT5 in Basic Trigger Mode), or internal PocketWizard receiver built in to your flash.) This is done by following the directions for the How to Configure the ControlTL Transmitter - HyperSync Flash Duration For Standard Channels section, and trying to eliminate clipping at your highest shutter speeds.

Note: Using Speedlites or the Einstein E-640 for HyperSync with HyperSync is feasible only at full power with these flashes because of their IGBT design. HSS/Auto-FP is suggested for users shooting above X-Sync with Speedlites.

Read the HyperSync Setup section for more detailed information on how to adjust HyperSync.

Highest Energy

Highest Energy attempts to get as much flash energy into the image as possible. This will reduce gradation at lower HyperSync speeds, however it can result in black bars or clipping in the frame at the highest shutter speeds. For many situations this can yield useful results as clipping can be cropped out of the image, or the clipping area is exposed by ambient light primiarily.

Highest Energy benefits photographers:

• Using HyperSync speeds just above X-Sync
• Who need as much action stopping flash power in the image as possible (remember that for HyperSync, longer flash durations are better)
• Where gradation is not acceptable
• In any situation where cropping is an option

"Highest Energy" is selected on the ControlTL receiver, as shown on the All ControlTL Radios – HyperSync Automation page.

• You can use Highest Energy-style HyperSync manually with a non-ControlTL compatible flash by following the directions for the FlexTT5 P2 Port and trying to eliminate clipping at lower HyperSync speeds without "clipping" visible at the bottom of your frame.
• You can attempt to use Highest Energy-style HyperSync manually with a radio receiving on a Standard Channel (meaning a (Plus II, Plus III, PlusX, MultiMAX, FlexTT5 in Basic Trigger Mode), or internal PocketWizard receiver built in to your flash.) This is done by following the directions for the How to Configure the ControlTL Transmitter - HyperSync Flash Duration For Standard Channels section, and trying to eliminate clipping at your lower HyperSync speeds without "clipping" visible at the bottom of your frame.

Note: Using Speedlites or the Einstein E-640 for HyperSync with HyperSync is feasible only at full power with these flashes because of their IGBT design. HSS/Auto-FP is suggested for users shooting above X-Sync with Speedlites.

Read the HyperSync Setup section for more detailed information on how to adjust HyperSync.

Factors to consider

There are many factors that may impact HyperSync performance.

Flash Duration

• Flash duration is a critical factor in HyperSync performance. The flash duration is the length of time from when your flashtube is first energized to when it is no longer emitting energy. Longer flash durations are better. You may want to compare t.5 times from flash manufacturers to see how long or short your flash is compared to others.

Power Level

• Flash duration is a critical factor in HyperSync performance. The flash duration is the length of time from when your flashtube is first energized to when it is no longer emitting energy. Longer flash durations are better. You may want to compare t.5 times from flash manufacturers to see how long or short your flash is compared to others.

Camera Choice

• Cameras with larger and slower shutters can produce more noticeable gradation. Cameras with faster moving shutters and smaller sensors can improve HyperSync success by minimizing gradation. Faster or slower moving shutters are not the same as your camera's shutter speed setting.

• Some cameras allow enough time for HyperSync to fire before the camera moves its first shutter. Some do not. Different combinations yield different results.

What HyperSync results can I get with my camera and flash?

Thankfully, we have done a lot of the work for you by sharing images that we have captured using as many combinations of camera and flash model as possible. Our examples are available below. Simply click on your camera and find the flash that you wish to use with HyperSync. There are countless combinations of flashes and cameras in the world, and we will add more cameras and flashes as time goes by. If you don't see your equipment, feel free to contact us directly: http://www.pocketwizard.com/contact/inquiry/

Read the HyperSync Setup section for more detailed information on how to adjust HyperSync.